AG,
> I've got the PDF on one of my computers. When I find it I'll
> post it up on the website.
>
> For most of my lens tests I printed out five of them and placed
> them in an "X" pattern so I can check center and corner
> resolution. Mount the lens to test and place the camera close
> enough to get all five charts squared up in the viewfinder. I
> also have a color/gray scale chart in there too for metering
> sanity. If at all possible, use flash to expose the charts. A
> studio flash with variable power output works very well. Just
> make sure the placement is such that you don't get flash
> reflection off the charts.
Thanks a lot for this. I am looking forward to trying it. I do wonder
how my Summicron, Jupiter, Planar and Zuikos will compare ... :-)
> First of all, with the 5MP digicam I DO experience a loss of
> resolution with filters. The 2/3" format is so "on-the-edge" of
> performance limits of the lenses that just about anything will
> skew the results.
This confirms related notes on filters on the web, for instance
http://medfmt.8k.com/bronfilters.html. I am always amazed when
people on the *bay sell lenses with dust, haze, scratches and
cleaning marks "that have no effect on picture quality".
> My resolution tests didn't prove much, other than an ideal
> analog setup (with extremely fine-grained film and flash
> exposure) outperformed the same test in 2/3" digital by 6-8
> steps. It was a benchmark test for my own sanity.
>
> However, it did prove something else. When enlarged to obscene
> sizes, the analog outperformed the digital because of the
> natural occuring artifacts (random by nature, and finer than
> what the lens was able to resolve. Digital, by comparison, is
> as sharp up to a limit. As soon as you hit that limit, it
> becomes unnatural and does not withstand further enlargement.
>
> I'm looking at an 8x10 at my desk, right now, taken with the
> digicam. It is, by far, the sharpest photograph you've ever
> seen, with details in places that I've never experienced before.
> However, at 11x14 it croaks. It's still sharp, but not
> pleasing. Absolutely worthless. In comparison, there is an 11x14
> B&W that isn't as sharp, but withstands enlargements of any
> size.
>
> 1. Grain is grain, but noise is noise.
>
> 2. Random grain is like sand--it's natural, expected, and easily
> ignored (or accepted) by the eye.
>
> 3. Digital noise almost always has a pattern--it's unnatural,
> unexpected, and not easily ignored (nor accepted) by the eye.
>
> AG
I am also wondering how much pixel depth affects resolution. Naiively
one might assume there is no impact. However, since before the discretization,
everything is analog, my guess is that perceived output resolution (what you
call
digital noise) of a scanner or digicam depends on
Information = #samples * #bits
even for B&W pictures. Did you see that ? In other words, when you reduce the
bit depth in photoshop from 16 to 8, the sharp cut-off you observe should
become more prominent or happen earlier.
All that does remind me of tube vs transistor amplifiers, or CD vs LP
discussions
we used to have 15 years ago ...
Thanks,
Roland.
=====
FeRider (R.)
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